linux-kernel - Re: [PATCH] linux-input: TSC-10 DM USB touchscreen driver assume 2-byte response from controller

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Date:	Tue, 11 Nov 2008 16:52:19 -0500
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Nuno Lucas <ntlucas@...il.com>, Daniel Ritz <daniel.ritz@....ch>
Cc:	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] linux-input: TSC-10 DM USB touchscreen driver assume
	2-byte response from controller

On Thu, Nov 06, 2008 at 03:25:40PM +0000, Nuno Lucas wrote:
> The usbtouchscreen module implements a driver for the TSC-10 DM USB
> touchscreen controllers, but assumes a 2-byte response for the
> CMD_RESET and CMD_RATE commands, when they can be only a single byte
> when no EEPROM is connected.
> 
> The driver worked with an earlier controller revision, but new
> revisions of the controller fail.
> 
> It seems the problem is that the early controller had the
> SEL4/EEPROM-CS pin high, but the new controller has it down, making
> the response different.
> 
> Without the fix, the controller would answer the single byte 0x06
> (ACK), making the init fail with -ENODEV because buf[1] is 0xFF (as
> initialized before).
> 
> As the single byte is the only thing we need to check it was ok, there
> is no need to verify the second byte.
> 
> The [0x15 0x01] case is the NAK [0x15] response for when there is no
> data in the EEPROM [bit-0 of second byte set], so I let that be, as I
> don't have any controller with an EEPROM.
> 
> With this patch, both the earlier and latest controller work the same.
> 
> Note: This was previously submited as BUG #11961 [1] on the bugzilla
> tracker, but rebased to version 2.6.27.4 and with unnecessary comments
> and printk's removed.
> 
> 
> Signed-off-by: Nuno Lucas <ntlucas@...il.com>
> 
> 
> [1] http://bugzilla.kernel.org/show_bug.cgi?id=11961

> diff -urNp linux-2.6.27.4/drivers/input/touchscreen/usbtouchscreen.c linux-2.6.27.4-patched/drivers/input/touchscreen/usbtouchscreen.c
> --- linux-2.6.27.4/drivers/input/touchscreen/usbtouchscreen.c	2008-10-25 23:05:07.000000000 +0100
> +++ linux-2.6.27.4-patched/drivers/input/touchscreen/usbtouchscreen.c	2008-11-06 15:07:49.000000000 +0000
> @@ -424,7 +424,7 @@ static int dmc_tsc10_init(struct usbtouc
>  	                      0, 0, buf, 2, USB_CTRL_SET_TIMEOUT);
>  	if (ret < 0)
>  		goto err_out;
> -	if (buf[0] != 0x06 || buf[1] != 0x00) {
> +	if (buf[0] != 0x06) {
>  		ret = -ENODEV;
>  		goto err_out;
>  	}
> @@ -437,8 +437,7 @@ static int dmc_tsc10_init(struct usbtouc
>  	                      TSC10_RATE_150, 0, buf, 2, USB_CTRL_SET_TIMEOUT);
>  	if (ret < 0)
>  		goto err_out;
> -	if ((buf[0] != 0x06 || buf[1] != 0x00) &&
> -	    (buf[0] != 0x15 || buf[1] != 0x01)) {
> +	if ((buf[0] != 0x06) && (buf[0] != 0x15 || buf[1] != 0x01)) {
>  		ret = -ENODEV;
>  		goto err_out;
>  	}

Daniel, have you seen this?

-- 
Dmitry
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